High speed automatic shutter mechanism and control



June 29, 1965 T. w. BATTERMAN ETAL 3,192,453

HIGH SPEED AUTOMATIC SHUTTER MECHANISM AND CONTROL Original Filed Sept.30, 1958 7 Sheets-Sheet 1 I08 I92 BLEEDER H2 no I06 THYRATRON j Tmmmm r's; BRIDGE I96 3 POTS 1456 POLARIZED I66 RELAY 227 RELAY z ,52 I34 INPUTI64 5 JUNCTION L BLOCK v E AND I 234 E CONNECTOR 260 BLADE 2- RELEASE 2POT BRAKE CLUTCH GEARS MOTOR LENOID ATT'YS J1me 1965 T. w. BATTERMANETAL 3,

HIGH SPEED AUTOMATIC SHUTTER MECHANISM AND CONTROL Original Filed Sept.30, 1958 7 Sheets-Sheet 2 N n F) 8 m u O 10 EN TORS:

June 29, 1965 T. w. BATTERMAN ETAL 3, 5

HIGH SPEED AUTOMATIC SHUTTER MECHANISM AND CONTROL '7 Sheets-Sheet 3Original Filed Sept. 30, 1958 FIG. 3A

BRIDGE BALANCED CUE SIGNAL ENDS t t2 TIME 6 O m m B Y 4 N N mmmm m E T TY A EMM R L L Y L Y EHE H mRT T BRAKE 58 6 45 mw OT TU O L M Cunuuuouoou FIG. 2A R viii -DUUOUUUDUUUUUUO INVENTORS. THEODORE W.BATTERMAN MATHEW POBOG BY W ATT'YS June 1965 'r. w. BATTERMAN ETAL3,192,458

HIGH SPEED AUTOMATIC SHUTTER MECHANISM AND CONTROL Original Filed Sept.30, 1958 '7 Sheets-Sheet 4 mwc v8 3m 5m mom mom INVENTORS: THEODORE W.BATTERMAN MATHEW POBOG BY [Mi 44 I ATT 'YS T. W. BATTERMAN ETAL HIGHSPEED AUTOMATIC SHUTTER MECHANISM AND CONTROL Original Filed Sept. 30,1958 June 29, 1965 '7 Sheets-Sheet 5 m ME T Wm a v a? ATT YS June 1965T. w. BATTERMAN ETAL 3,192,453

HIGH SPEED AUTOMATIC SHUTTER MECHANISM AND CONTROL Original Filed Sept.so, 1958 7 Sheets-Sheet 6 FIG. 7

INVENTORS: THEODORE W. BATTERMAN MATHEW POBOG BY 5: 2. M

ATT'YS J n 29, 1 5 T. w. BATTERMAN ETAL 3,192,458

HIGH SPEED AUTOMATIC SHUTTER MECHANISM AND CONTROL Original Filed Sept.30, 1958 '7 Sheets-Sheet 7 INVENTORS'.

THEODORE W. BATTERMAN MATHEW POBOG United States Patent 3,192,458 HIGHSPEED AUTOMATIC SHUTTER MECHANISM AND (IQNTRGL Theodore W. Eatterman andMathew Pohog, Danville, llh, assignors to Electric Eye EquipmentCompany, Danville, llh, a corperation of Delaware Original applicatienSept. 39, 1958, Ser. No. 764,331. Divided and this application Sept. 23,1960, fier. No. 57,985

11 Claims. '(Cl. Sid-28) This invention relates in general to settingarrangements for motion-picture printer shutters and the like such asdisclosed in application No. 764,331, filed September 30, 1958, nowPatent No. 3,046,864 of which this application is a division, and moreparticularly is concerned with a high speed automatic presettingmechanism and means for operating the same.

Motion picture film as used for display, that is, as finally producedfor projection is considerably different from the film which is obtainedby photographing scenes and developing the film. Disregarding theediting of the film which involves the insertion of titles and othereasily photographed portions and which involves excision and splicing ofthe film, one of the most important considerations of providing a finalproduct is the scene lighting. The

film which is produced by direct photography of scenes is rarely exposedunder optimum lighting conditions. In addition, many copies are usuallyneeded. The master film, as the original is called, is thus required tobe reproduced to provide copies, but in addition, in reproducing thesame the undesirable lighting conditions must be compensated for so thatthe final product provides the exact lighting conditions that the editorbelieves are necessary for proper projection of the copy. I

In the art of motion picture printing, copies of a master film areusually made by contact printing the master upon sensitized film,passing the engaged master and copy before a beam of light ofpredetermined intensity to expose the sensitized film, after which thecopy is developed. The quality of the print is controlled to a largeextent by controlling the intensity of the light beam to compensate forthe undesirable conditions of lighting of the master film. Such controlis essential for satisfactory film to be produced for proper projection.

It has become customary in the industry to produce the film in thefollowing manner: After the complete master has been put together, theeditor views the same carefully, scene by scene, and, using his bestjudgment, determines for each scene the best lighting conditions forprinting the same. These conditions are tabulated in any manner and themaster film is marked with identification means at each scene comprisinga cue to enable the printer operator to identify the scene and apply thelighting prescribed therefor. The scenes and their lighting conditionsare identified on the tabulation by the editor.

The intensity of lighting for the motion picture printing industry hasbeen to a great extent standardized in the United States, each degree ofintensity being represented by a number, and there being twenty-twodegrees of light numbered 1 to 22 inclusive, with the intensityincreasing with the value of the number. Zero represents a completeabsence of light, and the number 22 represents full intensity. Thus, inaddition to the different types of fade (which will not be discussed inthis specification), there are twenty-three variations of intensity ofthe beam of light to which the master and printed film are adapted to beexposed during printing operations. Such variations may be specified inany unrelated order from scene to scene, and it is required of Whatevermeans is used to print the motion picture film that it be capable ofmaking 3,192,458 Patented June 29, 1965 the necessary changes betweenscenes While the film traverses the beam of light.

The cues on the master film may take a variety of different forms, anyof which is suitable for use with the invention herein. Notches orperforations may open or close switches mechanically to give electricalcuing signals, or the particular scene may be identified by afiixing asmall bit of metal foil along the film edge and arranging the film topass a pair of contacts normally open which will momentarily be closedas the foil member passes to provide an electrical signal due to theclosing of the circuit by the foil.

Signals obtained from the cuing means have in the past been used to warnor notify an operator when to change the lighting conditions of theapproaching scene. Many different apparatuses have been used forprinting film, but in practically all cases, the film passes a fine irisat a continuous speed, and a beam of light is directed upon the iristhrough the use of any suitable optical system. Variation in lightintensity is obtained through the use of an arcuate shield or blade,hereinafter called shutter or shutter blade, which is swung to interceptmore or less of the beam of light. The said apparatuses have in the pasthad manually operable linkages to change the position of the shutterblade. The operator thus watches for the scene cues and consults thetabulation or chart he has for the lighting intensity. When he receivesthe signal, he will change a dial or move a lever or do some similar actwhich will be transmitted into shutter motion.

Present demands of those who use motion picture film have caused theseold methods of printing to be beset with many extremely disturbingdisadvantages. Where a motion picture subject runs for an hour or moreand scenes are lengthy so that the changes of lighting between scenesoccurred at widely spaced apart intervals, there is not a greatdifficulty in making manual changes of the lighting intensity. Theoperator in the past had plenty of time between scenes to assure himselfthat the setting for the next scene was properly made without error.This presumes, however, that even for these situations, the speed ofprinting was not so great relative to the length of film and the numberof scenes such that the operator would be pressed for time and henceliable to make errors.

The numbers and types of consumers of film have increased considerablybeyond the cinema hall owner and with such increase, the demands andrequirements of the motion picture film printing industry have increasedall out of proportion. Television, education and industry cannot usefilms of several hours duration. Shortness of time involved has givenrise to an unprecedented demand for short film subjects in which thescenes are likewise very short and must flash a quick and comprehensiblemessage. The manually operated printer cannot keep pace with thesedemands. An operator can make light changes with manual equipment atfilm printing speeds of not greater than 60 feet per minute and even atthis speed, where the scenes are less than a foot or more in length, itbecomes almost a physical impossibility for an operator to accuratelymake the changes in several such adjacent scenes. Short flashes intodays motion picture films are not unusual where' the length of filminvolved is one-half foot. The manually operated machine must beoperated at a very slow speed in order to enable such changes to bemade. At fast speeds errors and spoilage are a direct result of operatorfatigue and inability to keep pace with the scene changes commanded bythe master film. Since a great percentage of film used today is colorfilm, the expense of spoilage is increased greatly.

The speed of printing film is a direct measure of the profits to begained through the operation of the printer for reasons which arebelieved obvious. Slow speeds are inherent in manual printers, notbecause of the speed at which the film can be driven, but because of thelimitations of human skill and dexterity, and in addition because of theslow time required for the shutter to respond, due to inertia of theheavy and complex mechanisms and linkages heretofore used in printers.

Speeds of 150 feet per minute are impossible in a printer which isoperated manually, and yet such speeds are readily capable of beingachieved in apparatus con-- structed in accordance with the invention,even where the scenes are successively one foot long and the lightchanges are over the complete range of zero to 22. Longer scenes andshorter changes enable substantial increase in the speed of printing, upto 350 feet per minute.

The difliculties and disadvantages which have heretofore beset thisindustry provide an example of the type of situation wherein the presentinvention is intended to function and therefore it is illustrated ascontrolling a shutter to provide completely automatic operation in apicture printing system.

The invention may be considered from several standpoints which providethe general objectives above mentioned. The invention contemplates theprovision of a novel pre-setting mechanism which is here illustrated forpro-setting the position which a shutter blade will assume upon releaseand which is operated herein by suitable cam means; it contemplates anovel control circuit which operates in conjunction with a servo systemto properly position the cam means; it contemplates a novel servo systemarranged to operate with the control circuit and presetting mechanism;and it contemplates these structures in combination, not only withthemselves but with other metans to provide a system or systems by meansof which the advantages and most desirable features of the invention areachieved. Obviously, the combination of all of the structure to bedescribed hereinafter and which is illustrated is believed at this timeto give the best results, but even the use of portions of the systemwith other means will give rise 0 many benefits and advantages.

In connection with the systems above referred to, the shutterpre-setting mechanism and servo system may operate with a structureusing a pie-perforated tape passing through a suitable reader andproviding the control for positioning the cam means. This system wouldnot necessarily use the control system specifically described herein.Reference may be bad, if desired, to a co-pending application Serial No.764,330, filed September 30, 1958 by the applicants herein, and assignedto the same assignee as this application, now Fatent No. 2,923,354granted February 2, 1960, entitled Tape Perforator for a dis cussion ofthis manner of control. The particular system which is described hereinutilizes a programming board in conjunction with its control circuit andservo system in which the lighting conditions of consecutive scenes aremanually set up in a plurality of multi-position switches and the onesignal in addition to initiating the operation of the entire system,causes the switches consecutively to be energized or connected into acircuit as the scenes progress, thereby completing the properconnections with the control circuit for achieving the desired errorvoltage necessary to drive the servo motor. The details of thisprogramming board are shown and described in a copending application ofthe applicants herein, also assigned to the same assignee as thisapplication, Serial No. 768,687, filed October 21, 1958 and entitledAutomatic Programming Control Board for Automatic Shutters now PatentNo. 2,917,640, granted December 15, 1959.

The programming board is not discussed at great length hereinafter, andhence, some comment thereon would be advisable at this point. The servosystem of this invention is intended to rotate the cam means by a motorwhich also drives a potentiometer. A bridge compares the voltage acrossthe potentiometer and the voltage across a bleeder to achieve an errorsignal for energizing the motor. The bleeder has a plurality of taps,each representing a condition of lighting, and the taps are connected tothe same contact of each of the plurality of switches in the programmingboard. Thus, the number of contacts (all switches are the same)represents the different degrees of intensity, and the number ofswitches represents the number of scenes capable of being printed. Theslider of each switch is consecutively connected to the control circuitso that its setting with respect to its contacts will direct which tapof the bleeder will be involved. The consecutive connection of thesliders is accomplished by the cue signals.

Many objects of the invention and features thereof can be set forth atlength, but it is believed that these will become quite apparent tothe'one skilled in this art as he examines this specification, and inaddition, others will occur to him. It is desired, however, to point outa few of the features of the invention and its several phases other thanmentioned above which may serve as an aid to appreciation of theinvention:

The invention enables greater accuracy in placing the shutter andgreater repeatability of settings.

The invention saves considerable manpower.

The invention eliminates overshoot, errors, spoilage and the need foroperator skill.

The invention is readily embodied in apparatus which is simple tomanufacture and adjust; which is economical in initial cost andmaintenance and operation; and which occupies very little space.

The complete system has been described in considerable detailhereinafter as embodied in a commercial device, to comply with thepatent laws requiring a preferred example, and to further promote acomplete understanding of the invention, and how the same is used. Thisis exemplary, however, since almost infinite variation of minor detailsis possible without departing from the spirit of the invention.

Conventional symbols and pictorial diagrams are used to explain theinvention. While an attempt has been made to apply the referencecharacters in a systematic manner to avoid confusion, it must be pointedout that the numbers and letters of the terminals of the input andoutput plugs are not intended as reference characters, but merely toidentify terminals thereof. Like characters of reference in severalfigures of the drawings are intended to designate the same or equivalentstructures or means.

In said drawings:

PEG. 1 is a block diagram illustrating the control unit of the inventionand showing the general connections to the motor assemblage.

FIG. 2 is a diagrammatic block diagram illustrating the system of theinvention and showing the manner in which the system is used inconnection with a motion picture film printer.

FIG. 2a is a diagrammatic view of the system used to explain theoperation thereof.

FIG. 3 is a complete circuit diagram of the control unit of theinvention.

FIG. 3a is a chart showing the programming of the operation of thevarious parts of the system.

FIG. 4 is an exploded perspective view of the motor assembly of theinvention.

FIG. 5 is an exploded perspective view of the shutter operatingmechanism driven by the mot-0r assembly.

HG. 6 is a median sectional view taken through the entire assemblageincluding the motor and its associated parts as well as the shutteroperating mechanism.

FIG. 7 is an enlarged fragmentary eleva-tional view of the brakemechanism to show the details thereof.

FIG. 8 is an enlarged fragmentary View of the presetting mechanism foroperating the shutter.

FIGS. 9, 10 and 11 are similar views, comprising rear elevational viewsof the shutter operating mechanism showing the relationship between theparts for achieving three different positions of the shutter.

Attention is now invited to FIGS. 1, 2 and 3 in which aieaeee theoperation of the system is generally illustrated by means of block andcircuit diagrams. The basic system is best discussed in connection withPEG. 2 which illustrates the manner in which the invention ispractically applied to a system for printing motion picture film.

On the left hand side of KG. 2 there are illustrated four reels, 2d, 22,2d and 2d. The reels 2d and 2d are supply reels and the reels 22 and 26are take-up reels. A length of sensitized motion picture film is mountedon the reel Eli and threaded past .a suitable iris 23 and wound upon thetake-up reel 22. That portion of the sensitized film which extendsbetween reels 2% and 4.2 is designated 3d and it is in contact with asimilar length of film 32, the length 32 being a portion of the mastermotion picture film which is wound on the reel 24 and also extends pastthe iris 23 to its take-up reel 26. The film lengths 30 and 32 aretogether driven past the iris in complete contact so that light directedthrough the iris, along the path 34 will photographically affect thesensitized film as it moves past the iris, printing thereon the imagewhich appears on the master film.

Obviously the apparatus which supports the reels, drives them, andencloses the same in darkness, need not be shown since this may takemany different forms. The light source is symbolically illustrated at35, and suitable optical means are provided to concentrate the beam,including, for example, a parabolic reflector 33. The light beam 54 isintercepted by an arcuate shutter or diaphragm 4 the position of whichwill determine the amount of light which is directed upon the iris 28,and hence the amount of light that will impinge upon the contactedmaster film and sensitized film. This, therefore, provides a means forcontrolling the quality of the scene printed, to a certain extentindependent of the lighting conditions under which the scene wasoriginally photographed on the master film.

The technique described thus far in this specification is well known,and is in commercial use at the present time, there being certainstandards of lighting conditions established and accepted by theindustry for printing motion picture film. These standards aredesignated by the numbers 1 to 22, the light intensity increasing withthe increased value of number. Zero designates complete absence oflight, that is, the shutter completely cutting off the light.

Heretofcre, the position of the shutter has been adjusted by suitablemechanical means changed manually by a skilled operator. The master filmis provided along its edge with cuing marks or notches or pieces of foillocated at the scenes where the light conditions are to be changed.These have been chosen both as to scene and as to intensity of light bya film editor, and tabulated. The operator follows the tabulation andmakes the necessary shutter changes.

As previously mentioned, the operators speed is limited, and fdmspoilage and errors in li hting are not unusual. Tiedisadvantages ofmanual operation of the shutter are too well known to require discussionat length here. The invention is intended to eliminate the need for anoperator, eliminating errors in judgment and execution, enabling theprinting to proceed at a rapid rate completely automatically.

The reference character 42 designates generally an automatic'shutterassemblage with suitable parts which will shortly be explained, adaptedto be operated by a control unit shown in block form at 4 twhi-ch inturn is keyed or programmed by a. suitable programming board designatedgenerally as, The board 46 is the subject matter of the co-pendingapplication Serial No. 768,687, which has been mentioned above, andhence this application will make no detailed reference thereto. Thecontrol unit dd and the programming board 46 may be replaced by othermeans which will provide the required signals to the shutter assemblage4,2. For example, a perforated tape having the desired commands appliedthereto in the a form of groups of perforations in binary code may bepassed through a suitable reader to provide the signals applied to theshutter assemblage 42..

The invention herein has several different aspects in addition to theprovision of the shutter assemblage 42 and its mechanism. T cse includethe construction of the control unit 44, combination of such a controlunit with the shutter assemblage 42, and the combination-of the shutterassemblage d2, control unit 44, and some means for programming theshutter positions.

FIG. 1 is a block diagram of the shutter assemblage 42 and the controlunit 4%; FIG. 2a is a system diagram; FIG. 3 is a circuit diagram of thecontrol unit 44; hence the three figures should be consulted together inconnection With'the discussion thereof which follows immediately.

T he programming board as is connected to the unit 44 by means of acable 50 which, as shown, has approximately 32 conductors. Theconnection is made by means of one or more plugs, and it may be assumedfor illustrative purposes there is one such plug which engages asuitable socket in the unit 4-4. This connection is hereinafter calle aninput plug and is designated 5?. The output of the control unit isapplied in various manners to the assemblage 452 to change the positionof the shutter 4b. The various parts of the assemblage 42 which areinvolved are the motor 54 which provides the motive power for physicallydriving the pre-set mechanism which changes the position of the shutter;the electrically opera-ted clutch 56; the electrically operated brake53; a balancing potentiometer and a blade release solenoid 62. All ofthese last mentioned elements have parts which are mounted on the sameshaft and driven by the motor 5 except for the blade release solenoid62. The block diagrams include two other elements which are coaxial withthe motor shaft and these comprise the detent cup 64 and the gear box 66for reducing the speed of the motor. The detent cup operates inconjunction with a ball that is driven by the motor shaft, but this willbecome more apparent with the detailed description of the assemblage Wemay now consider the general problems which the apparatus is required tosolve and the functions which must be performed in order to solve suchproblems. The programming board 46 has been pro-set with certaininformation which relates to the desired dispositions of the shutter 49.At a given instant the shutter is required to assume a positionrepresented by the command of the programming board, and maintain thatposition throughout the entire extent of the scene that passesthereafter. At the end of the scene and the beginning of the next, theshutter again must move to a new position as cornmanded by theprogramming board and maintain that position, and so on.

and

The shutters position is adjusted by means of the motor 54 which iscoupled to the shutter through various mechanisms. Obviously the motormust be driven to rotate for a finite length of time between settings ofthe shutter which may be angularly a substantial distance apart. Inaddition, if the motor were coupled directly to the shutter, themovement of the shutter would provide a continuous change of light uponthe film as it passes, which is not acceptable because the effect mightbe similar to fade or gradual increase of light where a particularchange is desired. Both of these difilculties are eliminated bypre-loading or pre-setting of the mechanism which changes the positionof the shutter. The lighting conditions for one scene are pre-set in theshutter drive linkage while the previous scene is being printed. Inpractically all cases, the motor will have ceased rotating before saidprevious scene has been completed, and hence, when the command signal tochange lighting conditions is received, a solenoid will substantiallyinstantaneously release the shutter itself, to permit it to assume thepre-set condition, while the motor starts once more to 7 beginpro-setting the position of the next scene. in other words, each commandsignal performs two functions: (a) it operates a solenoid to release theshutter to the condition already pro-set, and (b) it starts the motorand drives the shutter pro-setting mechanism to the proper position forthe next command signal.

The sequence of these two occurrences is as stated above, and the systemis constructed so that the motor is not energized until after thecommand signal has been completed. The command signal actually isderived from the cue which is applied to the master fhm in the form ofthe notch, perforation or foil shown diagrammatically at 41 in FIG. 2a.

The motor is required to rotate an amount needed properly to positionthe shutter pro-set mechanism. This amount of rotation is controlled bythe information supplied by the program board, representing a setting ofthe shutter 40 to provide the light determined as proper by the editorfor the particular scene. The motor is therefore required to receive anerror signal, which must be polarized to drive the motor one way or theother from its former position to that which is to represent the propercondition of the preset mechanism. In order to do so, the motor alsodrives the slider of a balancing potentiometer and the voltage of thepotentiometer is compared in a bridge with the voltage derived from theprogramming board 46. When perfect balance is obtained the motor stopsrotating because the error signal becomes zero. The motor must beconnected to the potentiometer and the cup detent, and must be stoppedat precisely the instant that the desired condition is reached withoutovershoot, and hence there must be a sequence of clutching and brakingoperations which occur for each cycle of operation.

The sequence of operations is graphically illustrated in HS. 3a.

The apparatus must also provide means for effecting the performance ofvarious other functions, such as, for example, manually operating thedevice, starting and stopping the printer.

In FIG. 2a there is diagrammatically illustrated a system in which theprogramming of operations is achieved by means of a programming boardlike that of FIG. 2, designated 46, and specifically illustrated anddescribed in said patent application Serial No. 768,687, above mentioned. The general structure and operation of the system will bedescribed in connection with thi figure.

The master film has a cue-signal means in the form of a foil member 41or the like on an edge, and when the portion 32 of the master passes asuitable signal-producing device, such as an open electrical circuit orthe like, designated 4-3 in FIG. 2a, the solenoid 6?. is energized toinstantaneously change the shutter to some position determined by thepie-positioning or pre-set mechanism of the assemblage 42. The signal isapplied through one of the leads of the cable 50 to the control unit 44.Another signal is applied through the path designated generally 4-5 to astep-switch 47 operated by a solenoid 49 to move the arm 51 from onecontact to the next. Thus, it will be appreciated that each time thereis a cue signal, at the end of the cue signal, by virtue of therelaxation of a relay or the like, the step-switch 7 is moved one step.

The programming board has a plurality of manually adjustable rotaryswitches SW SW SW etc., there being as many switches as scenes it isdesired to provide the lighting for. Each switch has a plurality ofcontacts, which are designated C C C etc., there being as many contactsas lighting degrees, for example 23, and there may be another contactfor re-setting purposes, if desired. Only a few of these contacts areshown on each switch, and all of the identically positioned contacts areconnected together and to a suitabl terminal of the input plug 52 by aconductor of the cable The arms A A A etc. are each connected to one Uof the consecutive contacts CA CA CA etc. of the stepswitch 4-7. Theconductor 53 is the return of the arm 5'1 to the control unit 44.

Each step of the switch arm dll completes a circuit through a differentone of the switches SW SW SW etc. and since each switch arm A A A etc.is adjustable to any one of a plurality of different positions on thecontacts of that switch, the completed circuit will include only one ofthe conductors of the cable 50. The conductors leading from the contactsC C C etc. of the switches St l SW SW etc. each connect to a differcnttap of the bleeder '70 which is to be described hereinafter so that thevoltage thereby picked oil the bleeder 7h can be compared with thevoltage of the potentiometer 6%.

in this manner, an operator can position all of the arms of the switchesSW SW SW etc. in advance according to the editors tabulation of thedesired lighting for consecutive scenes, and turn on the equipment. Asthe master film passes the signal producing device 2-3, each time a cueiil passes it will change the shutter to any previously set position andconnect the next one of the switches SW SW SW etc. into the circuit.While the scene is being printed with the setting of the previouslighting condition, the pro-set mechanism is being adjusted to the newlighting condition, and as soon as the next cue 51 comes along, thecycle will repeat. in this manner the entire motion picture film can beprinted automatically. There are only physical limits to the number ofswitches that can be carried on the program board, and the same switchescan be connected to be scanned by the step-switch 47 a second time forlong films. After each cycle, which the step-switch 47 passing theconnection to the following of the manually changeable rotary switchesSW SW SW etc., the particular switch can be manually changed again sothat when the connection is made with it on the second round of thestep-switch, there may be a new setting thereof. All of this isexplained in said copending application.

The use of a pre-punched tape and reader will alleviate the need for theprogramming board 46 and control unit 44, but similar functions can beperformed by both with the assemblage 42.

Referring now to FIG. 3, the input junction block and connector 52 ofthe control unit 44 connects said unit by the cable Bil with theprogramming board 46. The control unit 44 has a bleeder 79 which isformed of a plurality of adjustable potentiometers all connected inseries and across a voltage source so that a particular voltage can bepicked and compared with the voltage of the potentiometer 6th. Thebleeder 76* has twentythree potentiometcrs which are designated P to Pinclusive, and which are separated, if desired, by other resistors whichare not designated by reference characters, the values and arrangementsof Potentiometers and resistors being such as to provide the desirederror voltage to drive the motor when compared with voltages of thepotentiometer The sliders or wipers of the potentiometers are connectedto twenty-three of the terminals of the input junction block andconnect-or 52, the lead from the slider of the potentiometer P beingconnected to terminal numbered 23, and the others being connected to therespective similarly numbered terminals, that is, P to terminal 1, i1 toterminal 2, and so on. Each of said terminals ii to 23 is connected toall of the identically positioned contacts of all of the manuallyadjustable rotary switches SW SW SW etc. so that the step-switch 4?serves to establish a connection with any pre-chosen tap P -P upon eachstep of movement. The negative side of the bleeder 1a is connected bythe lead '72 to the negative terminal of a power supply 74. The powersupply 7dincludes a transformer 76, the primary winding '75) of which isconnected to leads 8%) and 82 which extend respectively to the terminals31 and 32 of the input plug 52. The cable 5t includes two leadssupplying 115 volts A.C. power from a suitable source.

The center tap of the secondary winding $4- forms the negative terminal86, and there is a resistor and rectifier 83 and 99 in each of theterminals of the secondary winding 84, the opposite terminals of therecti tiers 88 and 9h beingconnected together to form the positiveterminal 92, a filter condenser 94 being connected across the terminalsas and 92. A low voltage secondary winding supplies filament voltage forthe two thyratr-ons of the circuit, which will be described.

The assemblage 42, comprising the motor 54 and related elements, isconnected to the control circuit 4 3 by means of a cable 9-6 which hasat least eleven conductors, the control unit 44 having a junction blockand connector 9% providingthe connection with said cable which will betermed the output junction block and connector. The terminals of thejunction block and connector )8 lead to various of the parts of theassemblage 42.

The positive side of the bleeder 7b is connected to the positiveterminal 92 of the power supply by the lead 1%. The potentiometer 6%also has a negative side and a positive side, and these are alsoconnected respectively to the negative and positive terminals S6 and 92of the power supply 74- through the cable 95, terminals C and A and theleads 1% and MP4. The center tap or slider of the potentiometer ccterminates at terminal B and this terminal connects by the lead 165 withthe right hand terminal 1% of the balancing, rectifying bridge 1%. Theopposite terminal 11d of the bridge 1% connects by the lead 112 to theterminal 255 of the input plug 52.

The terminal 23 extends to the common conductor 53 in the programmingboard 46 for all of the wipers or sliders of the potentiometers P to Pso that the voltages which are picked ofif the bleeder 7d and thepotentiometer 6d are compared at opposite terminals 1%, of the bridge1%. If the potentials are identical, there will be a balanced conditionof potentials applied to these opposite terminals of the bridge 108, butif the potentials are I different, current will flow in the bridge. itwill be noted that the bridge has four rectifiers 114, 115, 116, and 117and that all of the rectifiers are arranged so that no current can flowfrom the terminal 113, which is ground, to the terminal 119. There aretwo additional elements comprising resistors 12d and 122; which are inparallel respectively with the rectifiers and 1 17. The condition ofapplied potential balance is primarily detected by the solenoid 124which is connected across the terminals 1% and 1 16). As seen above, thebalance condition associated with bridge 1055 refers, in the context ofthe invention, to an equality of potentials applied to the oppositeterminals 166, 1 For conciseness of expression herein, the term balanceand unbalance as applied to the bridge 1th; will be understood tocomprehend, not a physical balance of impedances among the severalbridge arms, nor yet a physical balance of the mass of the bridge, butthe balance of the potentials applied to a pair of opposite bridgeterminals, as terminals 1%, 11d. Current will flow one way or the otherin the solenoid winding and will thus close a circuit from the lead 126through the relay arm 12% to either the contact 13% or the contact 13 2.This structure is referred to generally as a polarized relay and giventhe reference character 134.

As previously pointed out, since current can only flow in the bridgefrom the terminal'r119 to ground, in additi n to the unbalancing of thebridge causing the pol-arized relay to be thrown one Way or the other,the unbalancing of the bridge 103 will also cause a negative potentialto appear at the terminal 11%.

The terminals 1% and 132 are maintained at positive and negativepotentials respectively by a power supply which comprises atransformer-142 whose primary Winding 144 is connected across a suitableA.C. supply, the secondary winding 146 having one terminal connected itto ground and the other through two reversed polarity recti-fiers 143and 14% to provide negative and positive terminals 152 and 154respectively, The condensers connected to ground are for filteringripple.

Tracing the conductor 126 to the relay 156, the lead connects with thecenter arm 15% which is normally on the contact 1% connecting the lead126 to the solenoid 162 of relay 164 to ground through conductor 166.When the relay 156 is energized in a manner presently to be described,the arm 158 will move off the contact 16% and on to the contact 168,thereby connecting the lead 126 to the lead 170, which extends to theterminal D of the output plug 98. This terminal connects directly withthe electric motor 54 and depending upon the position of the polarizedrelay 134, energizes the motor to run forward or backward. The motorwindings obviously are connected to ground at their opposite terminals.v

The polarized relay 134 will be in a neutral position when the bridge108 is balanced and under these circumstances no voltage can be appliedto the motor 54.

Considering the condition of unbalance, when this -occurs, as when thevoltages tapped off the bleeder '70 and the potentiometer 6d aredilferent, the negative potential on the terminal 119 will cause apotential across the grid resistor 174 in lead 176 and will be appliedthrough the resistor 178 to the grid 179 of the grid-controlled gaseoustube 186). The thyratron 180 has its second grid 182 grounded to itscathode 184 and its plate 186 connected by lead 188 to the contact 1% ofthe lower group of contacts of the relay 156. The plate 186 is alsocoupled through a condenser 1&2 to the plate 194 of a second thyratron196. The first grid 198 of the thyratron 196 is connected by the lea-d2% to the arm 20-2 of the relay 164, and this arm is normally inengagement with the contact 204 which connects through a resist-or 2% ofthe negative terminal 12 of the power supply 140.

The other contact 2% of the relay 164 connects to the positive terminal1% through resistor 210. The second grid 212 of the thyratron isgrounded as is the cathode 2,14. The center arm 216 of the relay 156connects through a resistor 218 and capacitor 220 by the lead 22-2 tothe terminals H and K of the plug 98. Note that the lead 224 extends toa connection between the terminal 27 of the plug 52 to these terminals Hand K also. The terminal H provides positive potential (8+) to theclutch 5-6 and brake 53, and the terminal K provides the same positivepotential (B-|-) for a pre-set switch (see 313, FIG. 5) located at theshutter for manual operation of the shutter,

The output of the thyratron 196 is applied through resistor 226 in lead228 to the terminal I which is the clutch voltage terminal. Note thatthe plate 194 of the thyr-atron 196 is also connected by Way of lead 227through the solenoid 23d of the relay 156, and also through the seriesresistor 232 to the 13+ lead 222. Center arm 216 connects by lead 234with the terminal E of the output plug @8, and this applies theenergizing voltage to the brake 58.

Another relay 240 is shown which has its solenoid 24-2 (shunted byseries resistance and capacitance to prevent sparking) connected inseries with resistor 24 through lead 246 to the 13+ lead 224-, adaptedto be energized by the re-set signal from the programming board 46through terminal 24 and lead 248. The lower contact 25d of the relay245i is connected to lead 246, and the arm 252 connects by lead 254 toterminal 25 of the plug 52. This is a reset connection. The groundedsolenoid 256 is in circuit with switch 259 and operates relay contacts(not shown). The relay associated with these contacts is a latchingrelay automatically to shut the printer oil at the end of the run. Thisis done simply by means of a special circuit through the programmingboard.

As previously stated, the sequence of operation of the parts of theassemblage 42 is of considerable importance. The sequence is graphicallyillustrated in FIG. 3a which is a chart of function of variouscomponents of the circuit of FIG. 3 graphed against time. The solidhorizontal lines indicate the periods of time during which the variousparts are functioning.

let us presume, for example, that a cue signal has been given by a notch.or perforation of the master film closing an electrical circuit. Theshutter pre-set mechanism has previously been set to some position,representing, say a light intensity of 8 and the next intensity set atsay 2%. As the cue signal is applied to the program board, it energizesthe shutter blade release solenoid 62 through the terminal 26 of theinput junction block and connector 52 by way of the lead 26% whichconnects with the ter- 'rninal J of the output junction block andconnector 9@.

There is a manual switch or button 313 on the assemblage 42 by means ofwhich this same function can be accomplished. When the cue signal hasbeen completed, and the relay in the programming board which has beenoperated thereby has relaxed, and not until then, the circuit from thebleeder 70 is completed through the particular rotary switch of theprogramming board which is now connected in the circuit. Since thisswitch has been set at 20, the voltage which is picked off the bleeder'70 is that which exists at the slider of the potentiometer P Thevoltages of the bleeder is applied through the common lead 53 of theprogramming board 46, the terminal 28 of the input plug 52, and lead 112to the left hand terminal .110 of the bridge 108. Since the position ofthe previous set-ting of the shutter was for intensity 8, the voltagewhich is applied to the right hand terminal 1% of the bridge 1% is thatpicked bit by the slider of the potentiometer 60, and the result will bean unequal voltage applied to the opposite terminals of the bridge.

Since this occurs substantially instantaneously, the time of unbalancecausing the polarized relay 13:4 to swing in one direction or the otherdue to fiow of current through the solenoid 124 may be neglected. Theenergizing of the polarized relay 134 is therefore considered asoccurring at the time t It may also be assumed that the arm 128 willmove as shown in FIG. 3 to close the circuit between the lead 126 andcontact 132. This closes the circuit through the solenoid 162 of relay164 by way of the arm 158, contact 160 of relay 156, and the lead 166.These latter cont-acts of the relay 156 are normally in engagement. Whenthis occurs, arm 2G2 of relay 164 is drawn from its normally engagedcontact 264- (which had been applying a negative potential to the grid1% of the thyratron 1% keeping it in cut-off condition) and moved tocontact 208 thus applying a positive potential on the grid 1% of thethyratron 196 through the lead 2430 from the terminal 154 of the powersupply 14b, causing the thyratr-on to fire.

The elapsed time from t to t in FIG. 3a is the inertial time for therelay 164 to operate, and it is of the order of 6 milliseconds.

It will be noted that the above sequence occurs re gardlcss of whichdirection the unbalance of the relay 134 occurs. Herein lies therectifying nature of the bridge 108. This bridge has no alternatingcurrent applied hereto since, as elsewhere explained, alternatingcurrent supplied to the control circuit is rectified at terminals as,92. At the same time, regardless of the direction of unbalance, anegative potential is being applied to the grid 179 of the thyratron18th from the terminal 119 of the bridge 108 thereby keeping thisthyratron in out-oil condition for all time that there is an unbalance.

With the application of positive potential to the thyratron 196, thethyratron fires and full current fiows in its plate circuit by way ofplate 194, solenoid 230 and resistor 23 2, to its B supply by lead 224.Firing of this thyratnon 1% occurs at the time t in chart of P16. 3n,and as soon as this occurs the arm 153 is pulled from contact 16% ontocontact 1&8. The thyratron 1% continues to pass full current, due to thecharacteristics of such gas-tilled tubes, and the potential of the lead126 is now applied to the motor through the lead by way of the terminalD of the output junction block and connector 98. The motor commences torotate in the direction which is determined by the polarity of thevoltage chosen by the polarized relay 134. The time period from t to iis the time required for the relay 1% to close the contacts to the motor54. This is of the order of 10 milliseconds. The motor S iis thus shownto commence its rotation at time t The thyratron 1% also causes flow ofcurrent directly to the clutch 56 by way of the lead 223 and theterminal I through the resistor 226, but without delay, hence it may betaken that the clutch 56 is energized just prior to the rotation of themotor 54 commences, namely at the time t the motor being energized attime t The above discussed connections of the potentiometer 6d, brake58, clutch 5d, and motor 54 to the control unit of the invention areshown diagrammatically in FIG. 3. The several connections are made, asshown by Way of conductors included among the multiple conductors oflead 96, to junction block and connector 98.

The situation as thus far described obtains from the time t to the timet, which may be a period of several hundred milliseconds. The motor 54,clutch 56, relay 2134, relay 164, and the relay 156 remain energized solong as the unbalance exists in the bridge 108 and across the terminalsHt? and 1%.

Note that when the relay 156 is energized, it closes the circuit fromthe plate 186 of the thyra-tron by the lead 138 through the contact 190arm 216 and lead 234 to the terminal E of the plug 93 which extends tothe electric brake 58, This circuit is inoperative, however, because solong as there is an unbalance, there is a negative potential on the grid179 of the thyratron 180 and it cannot conduct. The circuit is preparedhowever for a speedy action the moment that the thyra-tron does fire.

Gradually the potential picked oh the potentiometer 60 by its sliderapproaches the potential of the slider of potentiometer P of the bleeder7% while driving the presetting mechanism of the shutter to thecondition of light intensity Zti. As soon as his condition occurs, thebridge 1% is in balance. The potential on the grid 179 of thyratron 1%becomes zero and thyratron 123$) fires at the time t immediatelyapplying the brake 53 through the already established circuitabove-described. The firing of the thyratron 18% drops the potential ofplate 194 of the thyratron 1% through the capacitive coupling 132, andthis lowering the potential of the plate 194 below that of the grid 1%momentarily is sufiicient to extinguish the flow of current of thethyratron 1%, which immediately de-clutches the motor 54 from thecamshaft through lead 223, and relaxes the relay 156.

The balancing of the bridge 1% moved the relay 134 to neutral position,cutting off the current to the motor 54 which may thus be taken astie-energized at time 13 The circuit constants of the relay 156 are suchthat it takes approximately 25 to 30 milliseconds before it throw iscompleted, and this time is that within which the brake is engaged toprevent rotation of the camshaft. The relay tee is completely relaxed attime t and this re-establishes the normal conditions of the relaycontacts. These include the brake circuit being open and the platecircuit of the thyratron iii-d also being open. This latter conditionextinguishes the thyratron, and the entire circuit is now ready for thenext cycle of operation.

In the meantime, the extinguishment of the thyratron 1% at time n, hasrendered ineffectual the connection of the contact 2% and the arm 2b.;and the solenoid 162 of relay 1M eventually is tie-energized at time tafter the delay of relaxation of the relay 1%. it is thus also ready forthe next cycle of o eration. Note that the brake is only energized ifthe clutch is de-energized.

Summarizing the cycle of operation by reference to FIG. 3, the bladerelease solenoid 62 is energized with the cue signal and the shuttermoves to a previously set position. This is done by a circuit includingthe conductor 260. Thereafter the voltage from the bleeder 70 and thevoltage from the potentiometer as are applied to opposite terminals ofthe bridge 1%, the connections being indicated generally in the blockdiagram by the lines 112 and 185. The polarized relay 134- now reflectsthe unbalance through connections from terminals 11% and 106. Relay 164-is next energized through contacts of relay 156 along path identified byconductors 126 and 166. Thyratron 196 now fires through connection 294and this energizes clutch 55 through connection 228 while energizing therelay 156 through connection 227. As soon as the relay 156 has completedits throw it energizes the motor 54 through connection 17d andestablishes a circuit to the brake 53 by Way of the lead 219, but thisdoes not energize the brake because the negative potential applied tothe thyratron 189 by the conductor 176 keeps it extinguished. As soon asbalanced condition is reached, at time t thyratron 18h fires,extinguishes thyratron 196 through the condenser 192, causes motor andclutch to be de-energized at time it; because of opening of relay 134,applies brake 58 through conductor 1&3 and relay 156, and when the relay156 is fully relaxed, becomes extinguished, de-energizing the brake andrelay 1%.

The above discussion has not considered certain parts of the assemblage42 which are deemed of substantial importance to this invention. Theseare illustrated in considerable detail in FIGS. 4 to 6 inclusive, andthe details of operation of the shutter blade itself are explained inconnection with FIGS. 7 to 11 inclusive- The various parts heretoforeidentified in FIGS. 1 to 3 inclusive carry the same referencecharacters.

The actual controlling device which positions the shutter blade 49 is acontoured cam 261, the radial distance from whose axis varies generallyaccording to the intensity of light to be permitted to pass the blade40. The mechanism which transforms the rotational aspect of the cam 261into proper relation of the presetting mechanism to accomplish thepositioning of the shutter blade will be for the present passed, and ineffect, the portion of the assemblage 42 to the right of the cam 261, asviewed in the figures, will first be explained.

The cam 261 is secured to a hub 262 which is mounted securely to thecamshaft 2&3 by a set screw or the like. The lefthand end of the shaftis journa'lled in the bearing 266 which is set into the memberheretofore termed a detent cup 64. The detent cup 64 is cylindrical inexternal configuration and is mounted in a split plate 267 which isprovided with a circular recess 2.68 to receive the same. A suitableclamping screw 269 may be taken up to contract the recess 26% to holdthe detent cup 64. The lateral extension 2759 of the recess 268 is topermit a portion of the cam 261 to pass through the plate 267 withoutinterference so that the portion of the assemblage 42 to the right ofthe plate 26?, including the cam 261, may be pie-assembled beforemounting in the plate 267.

The camshaft 263 has a collar 272 mounted thereon by means of a setscrew or the like, said collar being disposed on the interior of thedetent cup 64. Said detent cup d4 is cup-shaped, providing an interiorannular recess 273 within which a resilient arm 27d mounted on thecollar 222 is adapted to rotate. The arm has a ball seat 275 at its endwithin which there is disposed a hardened steel ball 276. The bot-tom ofthe cup 64 is provided with radial grooves 277 which are adapted tocooperate with the ball 276 in detent fashion, to perfectly position thecamshaft 263 and hence the cam 251i when a certain rotational aspect isreached. The system is capable of achieving a high degree of accuracy inplacement of the cam, but the addition of the detent mechanism rendersthe system even more accurate.

The detent cup 64 has the housing 278 of the potentiometer securedcoaxially therewith by means of the C-clamp 2 7d engaging in suitableannular grooves provided in each of the detent cup 6d and housing 278;the housing 278 has the housing 280 of the electric brake 58 securedthereto by means of a similar C-clamp 1281 engaging annular groovesprovided in the respective parts; the housing 280 has the housing 283 ofthe electric clutch 56 coaxially secured thereto by means of a similarC-clamp 2S4 engaging annular grooves. Each of the housings 278, 238, 283and the exterior surface of the detent cup 64 has the same diameter, sothat the resulting assemblage is in the form of an elongate cylinder ofsubstantially uniform diameter. The housing 283 has an elongatesleeve-like end extension 235 which is partially split as at 286, theresulting bifurcation adapted to be drawn together by suitable screws orbolts 287 whereby to engage the housing 238 of the gear box 66 of then10- tor 5d. The unitary motor and gear box assemblage is inserted intothe end of the extension 285 and clamped in place.

The motor shaft 239 carries a blade 2 which is axially engaged in agroove 2% provided in the stem 2% of the clutch rotor 22%. The clutchrotor 294 is of any suitable construction such as shown, in which thereis a ferromagnetic annular ring 295 separated from the stem and body ofthe rotor by a spacer 2% of some non-magnetic material such as anabrasive cement. The annular coil 2 when energized establishes amagnetic field axially to the left of the rotor 294 as viewed in FIG. 6,and thus seizes the annular ring 297 of ferromagnetic material and drawsthe same axially toward itself to complete the magnetic circuit acrossthe non-magnetic spacer 2% between rotor 294 and ring 295. Since thering 237 is spl'incd to a hub 25 9 that is fixed to the camshaft 263 byany suitable means such as a set screw or pin, the energization of theclutch winding 297 with couple the motor 54 to the camshaft 263 by anysuitable means such as a set screw or pin, the energization of theclutch winding 2%? will couple the motor 54 to the camshaft 263.

The brake 58 operates in substantially the same way that the clutchoperates, except that the winding 3% cperates in conjunction with anannular member fill that is constructed like the rotor 2% but has nostem, and which is fixed to the interior of the housing 2% by suitableset screws such as shown at 3G2. When the member 3&1 attracts its ring3%, also splined to the hub 2239, the camshaft 263 will be preventedfrom rotating. The two rings 297 and 303 are separated by a corrugatedspring 3% to keep the magnetic circuits apart and enable independentoperation of clutch and brake.

The potentiometer 6% has a rotor 3% which has one slider engaging a slipring fit-l7 and one slider engaging a resistance ring 3%. The electricalconnections of such a potentiometer are obvious.

Obviously electrical connections extend to the various electricalcomponents of the assemblage just described, and hence electricalterminals are illustrated in FIG. 4 but not given reference characters.The motor 54 and potentiometer 6% require three connections each, andthe brake and clutch each require two connections. The electricalconnections conveniently extend to the multiple connection plugs Sit)and 3 11 mounted on the arm 3 12 which also carries the pro-set pushbutton switch 313- for manual operation of the shutter.

The invention as described herein comprises several different phases,and the phase which is to be described in detail hereinafter is aportion of the system which is capable of being consideredindependently. It is based upon a structure which enables the positionof the shutter blade 4% to be pre-set without moving the shutter itself,

I so that when the scene whose lighting is represented by the pre-setcondition arrives at t e iris ed, the mere closing of an electricalcircuit effects substantially instantaneous movement of the shutterblade 40 to the new position.

As explained in connection with the control circuit, this same signal,or the completion thereof starts the apparatus upon the cycle ofpro-setting the linkages and mechanical connections to the nextcondition of the shutter. This latter cycle will usually take aconsiderably longer time than the time occupied in the quick movement ofthe shutter, and obviously such quick shutter movement is essential forhigh speed printing.

The camshaft 2.63 has as its ultimate purpose the rotation of the cam 261 to a particular radial disposition representing a position of theshutter blade. Thus, if such rotation of the earn 261 can beaccomplished by some other rotating shaft and drive-mechanism other thanthat described, satisfactory results will nevertheless be achievedthrough the use of the shutter pro-setting mechanism describedhereinafter. This mechanism is illustrated in FIGS. 5, 7, 8, 9, l and 11and that portion of FIG. 6 to the left of the cam 261.

The assemblage of detent cup 64, potentiometer 6i}, brake S, clutch 5d,and motor 54 is assembled as a substantially elongate cylindricalunitary structure and supported by means of the split plate 267 in therecess 268 thereof. This split plate is arcuate in configuration and ofsubstantial thickness to provide a relatively sturdy support. Said plate267 is secured to a circular plate 324 by means of a pair of spacers orposts 322 held in place by bolts 324 engaging through the plate 267,cylindrical recesses in the posts 322 and threaded into the right handface of the plate 326 as viewed in FIG. 6.

The top edge of the plate 326 is flattened at 326 to seat the arm 312which is suitably secured by fastening means such as machine screws 328.The edge of the plate 329 is rabbeted as at 330 to enable a cylindricalhousing 332 (FIG. 2) to be secured thereto by any suitable means, toretain the same dust-tight. The left hand side of the plate 326, whichcan be referred to as the exterior face, has an integral cylindrical hub332 which extends sub stantially outward therefrom, and a cylindricalring 334 split along its length at the bottom thereof at ass is clampedthereto by means of the screws 338. Approximately the upper half of thering 334 extends forward of the end of the hub 332 at 34%) and there isa substantially keystone-shaped blade guide plate 34-2 secured on theend thereof. An arcuate recess 344 coincides with the bore of the ring334 to clear the blade mount 3- .6 which is also split and secured tothe left hand end of the shaft 343 by clamping, using the screw 3%. Thehub 33?. is hollow and ball bearings 354 and 355 are disposed at theopposite ends thereof. The right hand end of the shaft 348 is enlargedproviding a hub 356 and a brake disc 35% integral with the shaft 348 andoverlying the inner face of the circular disc 320.

The blade 49 is arcua-te in cross section, the curvature lying on thecircumference of a cylinder whose axis is coincident with that of theshaft 348, and the blade extends axially outwar-d of the blade guideplate 342. Said blade is integral with a radial arm 36% at its righthand end as viewed in FIGS. 5 and 6 which is secured to the blade mount346 by suitable screws 362. A stiff arcuate member 364 is secured to theupper end of the guide plate 342 spaced therefrom a sufiicient amount topermit free arcuate movement of the blade arm 36b, and confining thearcuate movement of said arm between its extremities because of thespacers ass supporting the member 364. A flat arcuate leaf spring 36%engages against the blade arm 36%) to prevent wear of the arm ass toresult in looseness of the blade. Obviously if the extent of confinedmovement of the arm 3641 is not sufhcient for the purposes of theapparatus, the width of the arm 36d may be de creased or the width ofthe guide plate 34-2 increased.

The cam 261 has not been described in great detail since the contoursthereof will vary with the design of the structure. In the structureshown and described, the contours are perhaps best shown in FIG. 9 whichis a sectional view taken through the assemblage 42 on a plane just tothe right of the plate 267 of FIG. 6, but with the detent cup not shown.The view of the cam 261 is thus through the recess 268 of the plate 267and practically all of the cam 261 can be seen except for the part 3'70which forms one arcuate stop end 371 of the cam edge. The other stop endis at 372. The general contour of the cam edge is spiral so that therotation of the cam 261 will result in a changing throw of the follower,which increases or decreases with the rotation.

The cam follower link 374 is an elongate member which is slightly lessin length than the diameter of the plate 320. It is pivoted at 3:75 onthe upper end of a post 376 mounted on the inner face of the plate 3%.It is urged in a clockwise direction about its pivot 3'75 as viewed inFIG. 8 by means of a spring 377 one end of which is secured to the linkat 37%, a point which is adjacent its free end 37% the other end of thespring 377 being secured to a post 35% mounted in the end plate 320adjacent one of the spacers 322. About one-third of the Way from itsfree end 3'79 the link 374 mounts the cam follower 381 which is in theform of a roller mounted on ball bearings. As seen in FIG. 9, thefollower 331 will be moved in an are about the pivot point 375 withrotation of the earn 261. This will swing the link 374.

The free end 379 of the link 374 has an elongate slot 382 in which thereis disposed a roller 383 mounted on the end of the arm 385 of a T-shapedmember 386 which is part of an assemblage 3% referred to hereinafter asa double hinge.

The double hinge is formed of three parts, one of which is a member 3%,the second of which is the link 3%, and the third of which is theT-shaped member mentioned above. The member 392 includes a split sleevepart El /5 clamped to the hub 356 by the screw 396, having an integralrectilinear portion 397, which forms one of the leaves of the doublehinge. This rectilinear portion 397 at its right hand end (FIG. 8) has asocket or ear 399 which carries the hinge pin 4%, the axis of which liessubstantially on the plane of the edge of the rectilinear portion 397.The link 3% lies parallel with the portion 397 and at its right hand endhas an car 401 which includes a portion offset toward the portion 397and of lesser thickness than the body of the link 3%, so as to liebeneath the ear 399, and perforated to receive the hinge pin 400 also.The opposite, that is, left hand end of the link 394 is similarlyformed, but the offset ear 4-232 extends in the opposite direction, andhas a perforation lying on the plane of the bottom edge of the link 3%.The T-shaped memher 336 includes across bar portion 4% integral with theelongate center arm 385 which lies parallel with the link 3%, has an car4694 at its left hand end, and has a second hinge pin 405 pivotallysecuring said ear to the link 394.

As shown by the broken lines of FIG. 8, and by the views of FIGS. 9, 10and 11, the double hinge 390 can open to both sides of center. Lookingat FIG. 8, if the arm 335 swings to the right as indicated at 385',cross bar portion 4693 and the link 394 will remain engaged and togetherswing around the hinge pin 4%. If the arm 385 swings to the left, asindicated at 385", the link 394 and the rectilinear portion 397 willremain engaged and only the cross bar portion 403 will swing around thehinge pin 4495.

The end of the arm 335, in addition to the roller 383 also carries a pegor pin 4%, and between this pin 406 and a similar pin 4-97 which isprovided on the hub 356 at its center, there extends a helical spring408 which exerts a tension on the T-shaped member 386 tending to biasthe same toward the axis of the hub 356 at all times. This, of course,applies a constant force between the outer two parts of the double hinge3% always trying to close the parts of the hinge. If the T'shaped member386 of the hinge 3% has been moved to one side or the other and remainsin that position, the force in trying to bring the parts of the hingetogether Will also apply a component of force substantially at rightangle to the line between the pin lilo and the center of the hub 356,and this force is a vector whose direction is substantially tangentialto the hub 356, either one way. or the other. This vector also generallybisects the angle between the two open leaves of the double hinge. Theforce will therefore tend to rotate the hub one way or the other in anattempt to bring the three leaves of the double hinge together, andsimultaneously there will be a swinging of the T-shaped member 386 in adirection to bring its cross bar portion 4% to a position preciselynormal to the axis of the helical spring see which is a stable positionwhich comprises a radial line extending from the center of the hub 356to the peg or pin 4%. Obviously, in this movement, the roller 383 willmove along the slot 332. This movement, namely, the rotation of the huband jack-knifing movement of the T-shaped member 386 to close the leavesof the double hinge will occur only if the parts are disposed to permitsuch movement. This is normally prevented by means braking rotation ofthe hub as will be described, so that after movement of the cam, theparts will remain in poised or pre-set condition. 7 When released, thespeed of rotation of the hub, and hence the movement of the shutterblade it) depends upon the tension of the spring 408, the inertia ofthose parts which are required to move, and the friction of the movingparts and their shaftland pms.

Suitably balanced and mounted on bearings as shown at 354 and 355, thehub 356 and shaft 343 can be rotated almost instantaneously for the fewdegrees required, from a position in which the T-shaped member is movedone side or the other of a given center position.

It is important to understand that when the T-shaped member has beendisposed in a given position, the release of the hub 356 will result inthe double hinge 390 and its T-shaped member 3% assuming a new positionwhich is completely stable. Thereafter, the movement of the T-shapedmember to another position and subsequent release of hub 356 will befollowed by the movement of the double hinge and hub 356 to a new stableposition, and so on. Double hinge 3% may be considered a hinged link.

It should be seen that the rotation of the cam 261 is that which causesthe swinging of the link 374, the swing ing of the link 374 carries theroller 383 with it, the movement of the roller 383 applied to theT-shaped member would rock the link comprising the double hinge 3%directly to rotate hub 356 if the hub 356 is not restrained. Since thissituation does not obtain when cam 261 is being moved, the hub beingbraked, T-shaped member 336 is rocked one side or the other off part 392to produce the force vector mentioned. Since the hub 356 is notpermitted to rotate, the force tending to bring the parts of the doublehinge 3% together and change the position of shutter blade 40 will bestored in the spring 408, and whenever the hub 356 is released, the newposition of the shaft 343 will immediately be assumed. The dispositionof the shutter 49 can thus be pre-set and not permitted to change untilany time that is desired. The manner in which this is done will bedescribed next.

In FIG. 7 a braking mechanism has been illustrated without anyextraneous details to show clearly how the pre-set structure is heldagainst movement, and permitted to move whenever desired. The brakingdisc 358 is integral with the hub 356. A block 410 which is screwed tothe rear surface of the plate 32% has an undercut portion 411 withinwhich the end 412 of the brake arm 413 is adapted to rock. The brake arm413 is pivoted on a pin 414 carried by the block ilt and has a pressureedge 415 which is adapted to press the leaf spring 416 mounted on theblock 4149 against the edge of the brake disc 358. The spring 416 servesas a brake shoe. The mechanical amplification of the brake arm 413 isquite substantial since the distance from the pivot 414 to the pressureedge 415 is a small fraction of the distance from said pivot point tothe pin 418 at which point a helical coiled spring 4119 applies a forcetending to cause the pressure edge it; 415 to press against the edge ofbrake disc 358. The spring 419 extends between the pin 418 and the post380 to which, it will be recalled, the end of the spring 377 is alsosecured.

A bracket 429 secured to the plate 320 mounts the solenoid 62 whosemovable core 421 is bifurcated at 422, straddles a pin 423 in the end ofthe brake arm 413 and is prevented from being drawn past the pin 423 bya cross pin 4% extending between the halves of the bifurcation. Applyingcurrent to the solenoid d2 will pull the arm 413 against the force ofthe spring 419, relieving the pressure of the end 412 against the brakedisc 353. If the pre-set linkage has in the meantime been adjusted to aposition which would tend to rotate the hub 35d, mere application ofcurrent to the solenoid 62 releases the disc 358 and permits rotation ofthe shaft 343.

FIGS. 9, 1G and ill iiius rate the disposition of the parts of thepie-setting mechanism and the shutter for three different conditions.The cam Zl is shown only in PEG. 9 which is a condition of quiescence,that is to say, it is a condition in which the linkage or mechanism hasnot been pre-set or loaded to cause movement of the shutter blade Theshutter blade 45? shown in broken lines can be seen alignedapproximately with the upper right hand end of the cam follower link 375. The double hinge 390 is shown completely closed and hence theT-shaped memher is aligned with a radius through the center of the hub356. If the brake arm 413 were rocked by the action of the solenoid 62,nothing would occur to the shutter blade 4%). Note that the cam follower331 is located in the approximate center of the circumferential camsurface of the cam 261.

In FIG. 10, the earn 261 is not illustrated to keep the viewuncluttered, but it has been rotated in a counterclockwise directionapproximately to the end of its cam edge. This has brought the roller383. into the stop end which is closest to the axis of rotation of thecam. The link or arm has therefore been urged to follow the cam surfacein its decreasing diameter spiral by reason of the spring 377. The arm374 will therefore swing in a clockwise direction a slight amount aboutpivot 375. The initial position of the double hinge has been assumed tobe the same as that of PEG. 9. The slight movement of the arm 374 ismultiplied when this movement is transmitted to the end' of the T-snapedmember 336, and hence this member will rotate on the bottom pivot of itscross bar, opening only the outer leaf of the double hinge as shown. Nowwhen the solenoid 62 is energized, the T-shaped member 386 will rotateabout the hin e pin counter-clockwise, while the hub 356 and theremainder of the double hinge 390 rotate about the hub axis to close thedouble hinge. This will carry the hingle blade 45 to a new positionshown, displaced from its position in FIG. 9 in a clockwise direction.In FIG. 11, the same initial position as FIG. 9 is again presumed, butin this case, the cam 261 has been rotated in a clockwise direction toits opposite extreme, and the link 374 has been raised, swinging thesame slightly counterclockwise about its pivot 375 relative to itsposition in H6. 9. The double hinge 3% now opens in the oppositeirection from that of FIG. 10, the two outer leaves swinging together,and when the solenoid 62 is energized, the closing of the hinge willbring the shutter blade it) to a new position displaced relative theposition of FIG. 9 in a counter-clockwise direction.

Obviously the shutter is capable of being moved from the position ofFIG. 10 to that of FIG. 11 and vice versa, these being approximately theextremes of positions of the shutter blade. in the commercial deviceconstructed according to the invention, this maximum movement of theshutter blade occupied a time of approximately 3 milliseconds. Since thechanges which are made from scene to scene in printing film arepredominantly less than from extreme of lignt to complete absence oflight, the time occupied by the moving shutter will almost always beless than 3 milliseconds. Considering a speed at which the film can beprinted using the invention as approximately 150 feet per minute, themaximum amount of film which passes the shutter blade 4% during movementfrom extreme to extreme is .09 inch, which is a negligible fraction of aframe. Even for twice that speed, the total film movement is .18 inch.Such speeds of shutter change never before have been attained in thefilm printing art.

The commercial example also had a dead band of approximately threedegrees of rotation, this being the approximate maximum movement of thepotentiometer 65 which would not have any effect upon the servo system:

This means that the driving system, clutch, and brake lose control ofthe cam-shaft when the narrow dead band around the final light settingis reached by the cam-shaft. The detent mechanism then takes overmovement of the cam-shaft, and the ball falls into the bottom of thegroove closest thereto. Since the grooves are approximately 12 /2degrees wide, the repeatability of each setting is assured.

The pre-positioning mechanism of the assemblage 42 including both thedrive-clutch-brake-cam arrangement and the linkage and mechanism betweenthe cam 261i and the shutter blade 40 have achieved a high degree ofefficiency according to the invention, because of the elimination ofinertia to the greatest extent possible. The movement of theprepositioning linkage uses the shortest distance between the formerposition and that to which the same is adjusted. This is accomplished bythe double hinge arrangement which enables the cam follower link 374 toswing either side of the double hinge, thereafter to be followed by thereturn of the hinge and rotation of the shaft carrying the shutterblade.

Because of the speed possible with the invention, it is possible to haveshorter scenes, adequately and perfectly printed, completelyautomatically at speeds far exceeding any speeds which have utilizedapparatus heretofore known.

The many advantages which flow from the invention and all of the phasesthereof should by now be quite apparent to those skilled in this art,and many attributes not specifically mentioned will be manifest from theabove de scription. Further description is believed unnecessary since aneffort has been made to be as complete as possible in the disclosure ofall those details and principles of operation needed in order to afforda complete understanding of the invention and all parts thereof. It isdesired to point out what should also be obvious, namely thatconsiderable variation in the sizes, proportions, shapes, and many ofthe details of the invention, as well as in the electrical circuitrythereof, without in any way departing from the spirit or scope of theinvention, or sacrificing any of the advantages thereof. It is thereforedesired to emphasize that the invention is intended to encompass a widerange of equivalents all as intended by the patent law, limited only bythe language of the appended claims, interpreted in their widest scopecommensurate with the prior art relating to this subject matter.

What it is desired to claim is:

1. In a device of the character described, and which includes arotatable shaft whose position it is desired to control, an electricmotor adapted for forward and reverse rotation, an electric clutch whichwhen energized will couple the motor to said shaft, and a potentiometerincluding a rotatable element coupled to said shaft and adapted toprovide a voltage the value of which is related to the radialdisposition of said shaft; means for controlling the operation of saidmotor and clutch to rotate said shaft to a pre-determined position,which comprises: a voltage divider, means for tapping into said dividerat a position therealong representing said ire-determined position ofsaid shaft, a rectifying bridge having first and second opposite inputterminals connected, respectively, to the voltage of said tap and ofsaid rotatable element applied in balancing opposition thereto, apolarized cirwit-establishing device connected across balance terminalsof said bridge and energized only when there is an unbalance of voltagesrespectively applied to said opposite terminals and providing anunbalance current the direction of which depends upon the direction ofunbalance, a current make-break device having at least two output paths,one of which is directly to said clutch and the other of which is tosaid motor and having delayed switch means therein, the polarizedcircuit-establishing device being connected to initiate operation ofsaid makebreak device irrespective of polarity of said unbalance currentwhereby to activate said output paths, and said circuit-establishingdevice also being connected to said delayed switch means, whereby whensaid latter means is activated by said make-break device, said motorwill be energized, but only after a delay, to rotate in a directiondepending upon the polarization of said current, and only so long asthere is an unbalance.

2. A structure as claimed in claim 1 in which said make-break device isa grid-controlled gas tube, said delayed switch means is a relay, andsaid polarized circuitestablishing device is a polarized relay.

3. In a device of the character described, and which includes arotatable shaft whose position it is desired to control, an electricmotor adapted for forward and reverse rotation, an electric clutch whichwhen energized will couple the motor to the shaft, an electric brakewhich when energized will prevent rotation of the shaft, and apotentiometer including a rotatable wiper mounted on said shaft andadapted to provide thereat a voltage the value of which is related tothe disposition of said shaft; means for controlling the operation ofsaid motor, clutch and brake to rotate said shaft to a predeterminedposition, which comprises: a voltage divider, means for tapping intosaid divider at a position therealong representing said pre-determinedposition of said shaft, a comparison network having the voltage of saidtap and of said rotatable element applied in opposition therein and saidnetwork having an output circuit and providing a polarized current whosedirection and value are related to the difference between said twovoltages, circuit-establishing means in said output circuit adapted tobe energized only in response to an unbalance between the values of saidtwo voltages for producing a polarized current whose direction isdependent upon the direction of unbalance of the values of said twovoltages respectively applied to said opposite terminals, a firstcurrent make-break device having at least two output circuits, onecircuit being connected directly to said clutch and the other circuitbeing connected to first electromagnetic switch means, saidcircuit-establishing means being connected with both said firstmake-break device and said first electromagnetic switch means whereby toactivate said make-break device and cause thereafter energization ofsaid first electromagnetic switch means, said switch means whenenergized completing a circuit from said circuit-establishing means tosaid motor, whereby the condition of unbalance will energize said clutchand said motor, and a normally open electrical circuit connected toenergize said brake, a second make-break device adapted when activatedto close said circuit to energize the brake, means suppressingactivation of said make-break device so long as a condition of unbalanceof voltages applied to said two terminals exists, but causing activationwhen a condition of balance of said two voltages exists.

4. A structure as claimed in claim 3 in which said electrical circuitconnected to energize said break has a series switch therein connectedto be closed when said first electromagnetic switch means is energized,and said first electromagnetic switch means includes delay means, saidsecond make-break device having an extinguishing output connection withsaid first make-break device whereby to de-activate said firstmake-break device when said second make-break device is activated,thereby tie-energizing said first electromagnetic switch means andpermitting said brake to be energized while said delay means stillretains said series switch closed.

5. In a structure of the character described, a comparison circuit, anelectric brake, an electric motor, an electric clutch, a potentiometerhaving a rotor, a potentiorneter having an adjustable tap, a shaftmounting the rotor and clutch, the brake adapted to be energized toprevent rotation of the shaft, the motor adapted to be coupled to theshaft by energization of the clutch and drive the shaft thereby whensaid motor is energized, a suppression potential producing networkconnected with said comparison circuit, the rotor and tap beingconnected in balance arrangement to said comparison circuit andproviding a polarized error current if unbalanced, said networkproducing a suppression signal only when said current flows therein, apolarized relay and a source of negative and positive current adapted tobe connected to said relay when same is unbalanced, the relay beingconnected to be energized by said error current, a pair of gaseouscontrol tubes, one being connected to be activated by said error signaland the other connected to be suppressed by said suppression signal, arelay having first and second switches and the first tube connected toclose said switches, the first switch connecting said polarized relay tosaid motor and said second switch connecting the output of said secondtube to said brake, but said brake not being energized while said secondtube is suppressed, the first tube being directly connected to saidclutch, said second tube having its output also connected in suppressionrelation to said first tube, whereby when a condition of balance existssaid second tube will no longer be suppressed, but will becomeactivated, suppress the first tube while energizing said brake, and thesuppression of the first tube de-energizing said relay and opening saidswitches so that the brake is energized only for the short time requiredto de-energize the relay.

6. A structure of the character described for moving a shaft to apre-determined position, and which comprises, an electric motor, anelectric clutch adapted when energized to couple the motor to the shaft,an electric brake adapted when energized to prevent rotation of saidshaft, a potentiometer including a slider mounted on said shaft andconnected across a source of voltage whereby the voltage at said slideris a function of the shaft position, a voltage divider also across saidsource and having taps along the length thereof whose voltage varieswith position and is a function of the desired position of the shaft, arectifying bridge having first and second opposite terminals, means forconnecting said tap and said slider, respectively, to said first andsecond terminals, for causing flow of current between said terminalsresponsive to an unbalance between voltages respectively applied to saidterminals in a direction consistent with the sense of said unbalance,and a polarized relay connected in circuit with said terminals forenergization by current flow therebetween resulting from unbalancebetween said applied voltages, a first relay connected to be energizedby said polarized relay and a first thyratron having said clutch and asecond relay in its output, a motor energizing circuit adapted to beclosed by said first relay, the first relay being connected to fire saidfirst thyratron and thereby cause energization of said clutch and motorto rotate the shaft and slider while bringing the voltages applied tothe opposite terminal of said bridge to balanced condition, a secondthyratron having said brake connected in the output thereof through saidsecond relay, a suppression signal producing device connected with saidbridge and adapted to provide a suppression signal to prevent firing ofsaid second thyratron until a balance condition is achieved, the firingof said second thyratron acting to energize said brake, said secondthyratron also being connected to extinguish said first thyratronwhereby firing of said second thyratron also de-energizes said secondrelay to de-activate said brake, the brake being thus activated onlyduring the time required for the second relay to respond to saidde-energization of said second thyratron.

7. In a device of the character described which comprises a servo systemincluding a shaft adapted to be positioned to represent a pre-determinedcondition, a motor connected to drive said shaft and an error signalproducing circuit to energize the motor including a potentiometer sliderdriven by said shaft, said system having a zone of no response withinwhich movement of said potentiometer slider will not result inenergization of said motor; detent means for accurately positioning saidshaft comprising a rotary detent member mounted on said shaft rotatingrelative to another detent member, one of said detent members having aplurality of radially arranged detent positioning means and the otherbeing of configuration to engage said positioning means, the polardimension of said zone being substantially less than the polar dimensionbetween detent positions whereby the final position of said shaft willbe controlled by the physical engagement of said rotary detent with oneof said positioning means.

8. A structure as claimed in claim 7 in which said one of said detentmembers comprises an annular disc having a plurality of radial grooveson a face thereof and said other of said detent members comprises a ballbiased against said face and adapted to engage in said grooves, and theball and disc being rotatable relative one another on the same axis.

9. In a device of the character described which comprises a servo systemincluding a shaft adapted to be positioned to represent a pre-determinedcondition, a motor connected to drive the shaft and an error signalproducing circuit to energize the motor including a potentiometer sliderdriven by said shaft and said system having a zone of no response withinwhich movement of said slider will not result in energization of saidmotor; detent means for accurately positioning said shaft comprising amember having a plurality of radial V-shaped grooves mounted coaxialwith said shaft but the shaft being rotative relative thereto, ballmeans carried by said shaft and resiliently biased against said groovedmember to be engaged in said grooves consecutively as said shaft rotatesand thereby accurately position said shaft, and the polar dimensionbetween grooves being greater than said dead zone.

10. A structure as claimed in claim 9 in which the grooves areimmediately adjacent one another whereby in moving from groove to groovesaid ball means must ride over a sharp ridge.

11. A presetting arrangement wherein an object is movable to any one ofa plurality of positions for exercising a different control function,the improvement comprising a single prepositioning means, a rectifyingbridge circuit, a programming means for successively applyingdistinctive control voltages to said bridge circuit for energizing saidsingle prepositioning means, while said object is performing saidfunction, to move said prepositioning means to any one of a plurality ofdifferent positions, and means thereafter controlled by saidprepo'sitioning means for moving said object to a respective positioncorresponding to the last named position of said prepositioning means.

References Cited by the Examiner UNITED STATES PATENTS 2,715,703 8/55Schuck 318162 2,840,771 6/58 Kammn 318-28 2,917,640 12/59 Batterman etal 318-29 X 2,991,762 7/62 Baumback et al. 318-162 JOHN F. COUCH,Primary Examiner.

ORIS L. RADAR, MILTON O. HIRSHFIELD,

Examiners.

1. IN A DEVICE OF THE CHARACTER DESCRIBED, AND WHICH INCLUDES AROTATABLE SHAFT WHOSE POSITION IT IS DESIRED TO CONTROL, AN ELECTRICMOTOR ADAPTED FOR FORWARD AND REVERSE ROTATION, AN ELECTRIC CLUTCH WHICHWHEN ENERGIZED WILL COUPLE THE MOTOR TO SAID SHAFT, AND A POTENTIOMETERINCLUDING A ROTATABLE ELEMENT COUPLED TO SAID SHAFT AND ADAPTED TOPROVIDE A VOLTAGE THE VALUE OF WHICH IS RELATED TO THE RADIALDISPOSITION OF SAID SHAFT; MEANS FOR CONTROLLING THE OPERATION OF SAIDMOTOR AND CLUTCH TO ROTATE SAID SHAFT TO A PRE-DETERMINED POSITION,WHICH COMPRISES: A VOLTAGE DIVIDER, MEANS FOR TAPPING INTO SAID DIVIDERAT A POSITION THEREALONG REPRESENTING SAID PRE-DETERMINED POSITION OFSAID SHAFT, A RECTIFYING BRIDGE HAVING FIRST AND SECOND OPPOSITE INPUTTERMINALS CONNECTED, RESPECTIVELY, TO THE VOLTAGE OF SAID TAP AND OFSAID ROTATABLE ELEMENT APPLIED IN BALANCING OPPOSITION THERETO, APOLARIZED CIRCUIT-ESTABLISHING DEVICE CONNECTED ACROSS BALANCE TERMINALSOF SAID BRIDGE AND ENERGIZED ONLY WHEN THERE IS AN UNBALANCE OF VOLTAGESRESPECTIVELY APPLIED TO SAID OPPOSITE TERMINALS AND PROVIDING ANUNBALANCE CURRENT THE DIRECTION OF WHICH DEPENDS UPON THEDIRECTION OFUNBALANCE, A CURRENT MAKE-BREAK DEVICE HAVING AT LEAST TWO OUTPUT PATHS,ONE OF WHICH IS DIRECTLY TO SAID CLUTCH AND THE OTHER OF WHICH IS TOSAID MOTOR AND HAVING DELAYED SWITCH MEANS THEREIN, THE POLARIZEDCIRCUIT-ESTABLISHING DEVICE BEING CONNECTED TO INITIATE OPERATION OFSAID MAKEBREAK DEVICE IRRESPECTIVE OF POLARITY OF SAID UNBALANCE CURRENTWHEREBY TO ACTIVATE SAID OUTPUT PATHS, AND SAID CIRCUIT-ESTABLISHINGDEVICE ALSO BEING CONNECTED TO SAID DELAYED SWITCH MEANS, WHEREBY WHENSAID LATTER MEANS IS ACTIVATED BY SAID MAKE-BREAK DEVICE, SAID MOTORWILL BE ENERGIZED, BUT ONLY AFTER A DELAY, TO ROTATE IN A DIRECTIONDEPENDING UPON THE POLARIZATION OF SAID CURRENT, AND ONLY SO LONG ASTHERE IS AN UNBALANCE.